Helical gear pump with stator compression



Feb. 24, 1959 J. D. BOURKE 2,874,643

HELICAL GEAR PUMP WITH STATOR' COMPRESSION Filed Oct. 15, 1957 INVENTOR. a5, ,Erwa Bade ATTORNE N M MN ham 3.

2,874,643 iasreniedi aebsas,.1959

HELICAL GEAR? PUMP --WI'I H" STATOR 'COMPRESSION' .l ohn David Bourke springfield, Ohio, assignor to: Rob- & Myers, Inc.,,Springfield, hio,.a corporationot 7 i0 ApplicatlonOctober 15,1957, Serial N02 690,241

*sgcnnm. cl. mat-+117 Thisflinvention relates to rhelical i gear pump of, the; type .inventedbyeR. r J. "L..1Moineau, wherein, a; 2 helieally' externally lthreaded rotoracoacts with" an;- internally helically threaded stator said stator having. one,v .morethread. than said rotor. .Pumps of this general type are:now-generally built with a metallic. rotor-which is rigid and ;a. stator which is of flexible or resilient material such as .rubber. Pumps. of this type. .are, particularly advantageous in. the handling of abrasive .materialsg However; the. abrasive materials produce wear and this wear ismsuallygreatest .towardthe discharge end of the pump. v

In my earlier Patent No..,2, 796,029, dated June 18, 1957, I disclosed and claimeda pump whereina metallic semi-cylii'idrical element was interposed betweenthe stator and the ca'sirigicin fwhihttheistatonwas disposed and -wherein anwadjusting screw was .provided whereby the .stator could be compressed to a desired degree; .It was statedto be. an object of the invention to PIOVldG'gSUCh adjusting means which would be self-aligning so. that-the adjustment'would compensate for increased wearrtoward --one end of the pump or the other. ,It.vvas alsosstated to be an object ofthe invention to make it possible to increase the capacity of such a pump at higher pressures and to provide a pump where the maximum efiiciency would occur at higher pressures.

All of the above mentioned objects are also objects of the present invention. Additionally, it is an object of the present invention to provide an improvement over my said earlier patent whereby the stator is compressed by fluid pressure and to provide a means whereby the stator may be subjected to the, discharge "pressure of the pump so that as the discharge pressure increases, the stator is more greatly compressed.

These and other objects of the invention which will be pointed out hereinafter or which will be apparent to one skilled in the art upon reading these specifications I accomplish by that certain construction and arrangement of parts of which I shall now describe certain exemplary "embodiments.

Reference is made to the drawings forming a part hereof and in which:

Figure 1 is an elevational view partly in longitudinal cross-sectionshowing one embodiment of the invention.

Figure 2 is a cross-sectional view taken on the line 2-2 ofFigure 1.

Figure 3 is a view similar to Figure 1 but showing another embodiment of the invention.

Briefly, in the practice of the invention, the external pumping element, i. e. the stator, is disposed Within a casing member and is fitted snugly therein. The casing member is relieved over the entire length of the stator anda rotor element Ill-driven by: meausaot ashaft; t11..,from

.. a helical motor -(not e'ShOWIl) .E 'As fis known ill: the. art, :the rotor is connected to?the;shaft lla bymeansof a .;double universal; joint to permit the. rotor- 10a to orbit in a cylindrical path.

. The rotor 10-coacts'purnpingly with a.-stator;-11-twhich 2is made'of rubber or other suitable flexible and resilient material. The stator 11 is provided -with the-,endt;flanges F 12 andis seated within'z'a casing element 13 havingthe 10 indi'cated' generally -at';.-16,. is; ,provided.avith aPflflDgeyU end flanges. 14 and-.15. The intake-.memberaoftheppump sand the flanges 14-ar1d17*.are,rabbeted:to receive the rflange' 12 of the stator-which isaclamped therebetween haust fitting 18 is provided with a flange;19gand-.the flanges '15 and 19.-are;- rabbeted to receive the other stator ;flange .12-whichis;elamped-therebetween.

. The 'casingtelement, 13 is relieved-at 201 to; provide the .fluid chamber mentioned; above; and which, 138, .seen; in 20 and t-whichaas-t seen in Figure .2, "isrof substantialtwidth.

- Thestator1 11 at ,least overtthe area: exposed; to? the cham- =-,ber-. 20 is reinforced as indicated at;2 1. This-reinforcementxmay consist of anysuitable areinforci-ng-gmaterial Figure .1,: extends asubstantially -.the length {of the stator molded into or embedded in the material of the statonor titv may. comprise a ,meta-llic rigid. shim-permanentlybonded tothestator. In the embodiment illustrated in thetdrawembodiment illustrated is ot semi-cylindricalformxandJ-is permanentlybonded :by --any suitable means ,to the vtstatgn- 11. The purpose of the reinforcement is to prevent collapse of. the stator. membersll into.the ptunping-pockets ber 20 the stator is uniformly,cqrnpressedswithql t the danger of producing a collapse as above described.

While pressure may be applied to the chamber 20 in any desired manner, either hydraulically or pneumatically, by means of a separate pump or compressor, I have found it particularly desirable to obtain the desired compression from the discharge pressure of the pump. Thus, in Figure 1 the exhaust fitting 18 is provided with a passage 23 and a passage 24. The casing element 13 is provided with a passage 25 and a passage 26. The passage 23 communicates between the pump discharge and the passage 24. When the pump is assembled with a suitable gasket 27 the passage 24 is in communication with the passage 25 which in turn communicates with the passage 26, which itself is in communication with the fluid chamber 20. Thus, as indicated by the arrows in Figure 1, when the pump is running, a portion of the discharge passes through the passages 23 to 26 inclusive and into the chamber 20 and the chamber 20 will be thereafter maintained at the discharge pressure of the pump.

The embodiment of Figure 3 does not diifer substantially from the embodiment of Figure 1 except that the discharge fittiug 18a communicates with a cylinder 30, which 7 cylinder at its other end communicates through the tubing 31, 32 with the chamber 20. A floating piston 33 is provided in the cylinder 30 and the volume above the piston 33 and including the tubing 31, 32 and the cham-- ber 20 is filled with suitable fluid.

In this embodiment of course, the discharge pressure of the pump operates against the piston 33 which trans- -.mits the pressure to the fluid 34 which in turn bears against the shim 21.

' While I have shown the direct use of discharge pres- I have found that with a device such as shown in the drawings the output of the pump holds up far better under increased discharge pressure. For example, a standard pump without the invention disclosed herein and which will pump 6.9gallons per minute against zero discharge pressure, the discharge volume drops to about 6.5 gallons pef minute at pounds discharge pressure, to 6.1 gallons per minute at pounds discharge pressure, to 5.4 gallons per minute at pounds dis charge pressure, to 4.4 gallons per minute atpounds discharge pressure, to 3 gallons per minute at pounds, and to 1.4 gallons per minute at pounds per square inch discharge pressure. v

I The same basic pump modified as taught herein and delivering 6.9 gallons per minute at zero pressure will deliver 6.7 gallons per minute at 50 pounds, 6.4 gallons per minuteat 75 pounds,-6.1 gallons per 'minute at 100 pounds,- 5.6 gallons per minute at 125 pounds, 5.1 gallons per minute at 150 pounds and 4.4 gallons per minute at 175 pounds.

A remarkable change also takes place in the efficiency of the pump. The same standard pump described above operated at 100% of peak efficiency against the discharge pressure of 110 pounds per square inch and with an increase in discharge pressure the efficiency droppediolf rapidly and was down to 75% of peak efliciency at 145 pounds discharge pressure, down to 50% of peak efiiciency at 165 pounds discharge pressure, and down to 25% of peak efiiciency at pounds per square inch discharge pressure.

Modified as herein disclosed, the pump exhibited maxi-- mum efliciency at 125 pounds per square inch discharge pressure and maintained substantially peak efficiency up to 150 pounds per square inch discharge pressure and efliciency only dropped to about 85% of peak elficiency at pounds dischargepressure.

It will be clear that various modifications may be made without departing from the spirit of the invention and I therefore do not intend to limit myself except as set forth in the claims which follow.

Having now fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a helical gear pump having an externally helically threaded rigid rotor, an internally helically threaded stator of resilient material pumpingly coacting therewith, and a rigid casing element within which the said stator is retained; said casing element being relieved internally over substantially its entire length to provide a fluid chamber of substantial angular width external to said stator and extending substantially the entire length of said stator, reinforcing means for said stator extending throughout its length and to an angular width greater than the said chamber in the region exposed to said chamber, and means for applying fluid pressure to said chamber.

2. A pump according to'claim 1, wherein said last named means comprises a fluid connection between the discharge of said pump and said chamber, whereby said chamber is at substantially the pump discharge pressure.

3. A pump according to claim ,1, wherein said last named means comprises a cylinder, one end of which is in communication with the discharge of said pump, a piston in said cylinder, the other end of said cylinder being in communication with said chamber, and a body of fluid filling the volume between said piston and stator, whereby said chamber is at substantially the pump discharge pressure.

4. A pump according to claim 1, wherein the reinforcement of said stator comprises a substantially semi-cylindrical rigid shim.

5. A pump according to claim 4, wherein said shim is permanently bonded to said stator.

References Cited in the file of this patent UNITED STATES PATENTS 2,527,673 Byram Oct. 31, 1950 2,691,346 Conery Oct. 12, 1954 2,695,694 Seinfeld Nov. 30, 1954 2,739,650 Hill Mar. 27, 1956 2,765,114 Chang Oct. 2, 1956 2,796,029 Bourke June 18, 1957 

